Can you not collapse them at all or do you mean that they uncollapse after a refresh?

The latter might have to do with HN storing this collapse-state in a Cookie/localstorage/similar and Firefox Focus throwing these sorts of things semi-regularly away to protect privacy.

It does not throw away the login-Cookie, so I'm not entirely sure how it works. They might even have a whitelist or (in this case erroneous) blacklist for it.

I find the hit target really small on regular Android Firefox too. It often takes me multiple attempts to get comments to collapse.

are you blocking javascript? hn is very good about not needing it for the site to function basically, but i think collapsing comments is one of few things it needs it for.